Rotation sensor

Abstract

The present invention allows for miniaturization of a rotation sensor. A rotation sensor (1) is a sensor for detecting the rotation angle of a rotating object (4). The rotation sensor (1) comprises a rotor (2) and a stator (3). The rotor (2) is conductive, is attached to the rotating object (4), and rotates as one with the rotating object (4). The stator (3) comprises a substrate (31), an excitation coil (32), a detection coil (33), an electronic component (34), a wiring pattern part (35), and a ground conductor (36). The substrate (31) has a first main surface (301) facing the rotor (2) in one direction (D1) and a second main surface (304) opposite the first main surface (301). The electronic component (34) is disposed on the second main surface (304) of the substrate (31). The wiring pattern part (35) is electrically connected to the electronic component (34). The ground conductor (36) is disposed between the rotor (2) and the wiring pattern part (35) in the one direction (D1).

Description

Rotation Sensor

[0001] The present disclosure relates generally to a rotation sensor, and more particularly to a rotation sensor that detects the rotation angle of a rotating object.

[0002] Patent Document 1 describes a rotation sensor that detects the rotation angle of a rotating object. The rotation sensor described in Patent Document 1 includes a rotor and a stator. The rotor is conductive and is attached to the rotating object to rotate integrally with the rotating object. The stator faces the rotor in one direction. The stator includes a substrate, an excitation coil, and a detection coil. The substrate has a facing surface that faces the rotor. The excitation coil is annularly arranged on the facing surface of the substrate so as to follow the outer edge of the rotor in a plan view from one direction, and generates a magnetic field. The detection coil is arranged inside the excitation coil on the facing surface of the substrate, and detects changes in the magnetic field. Furthermore, electronic components that constitute the circuit of the rotation sensor are arranged on the facing surface of the substrate.

[0003] International Publication No. 2023 / 149063

[0004] However, in the rotation sensor described in Patent Document 1, space must be secured on the board to place the electronic components, which increases the area of ​​the board and results in a problem in that the rotation sensor becomes large.

[0005] An object of the present disclosure is to provide a rotation sensor that can be miniaturized.

[0006] A rotation sensor according to one aspect of the present disclosure is a sensor for detecting the rotation angle of a rotating object. The rotation sensor includes a rotor and a stator. The rotor is electrically conductive and attached to the rotating object to rotate integrally with the rotating object. The stator faces the rotor in one direction. The stator includes a substrate, an excitation coil, a detection coil, electronic components, a wiring pattern portion, and a ground conductor. The substrate has a first main surface facing the rotor in one direction and a second main surface opposite the first main surface. The excitation coil is disposed on the first main surface of the substrate and generates a magnetic field. The detection coil is disposed on the first main surface of the substrate and detects changes in the magnetic field. The electronic components are disposed on the second main surface of the substrate. The wiring pattern portion is electrically connected to the electronic components. The ground conductor is disposed between the rotor and the wiring pattern portion in one direction.

[0007] According to the present disclosure, it is possible to reduce the size of the rotation sensor.

[0008] FIG. 1 is a front view of a main portion of a rotation sensor according to an embodiment. FIG. 2 is a perspective view showing the appearance of the rotation sensor according to an embodiment. FIG. 3 is an exploded perspective view of the rotation sensor according to an embodiment. FIG. 4 is a plan view of the surface of the rotor of the rotation sensor according to an embodiment. FIG. 5 is a plan view of a rotor used in the rotation sensor according to an embodiment. FIG. 6 is a first cross-sectional view of a substrate used in the rotation sensor according to an embodiment. FIG. 7 is a second cross-sectional view of a substrate used in the rotation sensor according to an embodiment. FIG. 8 is a plan view of a first layer of a substrate used in the rotation sensor according to an embodiment. FIG. 9 is a plan view of a second layer of a substrate used in the rotation sensor according to an embodiment. FIG. 10 is a plan view of a third layer of a substrate used in the rotation sensor according to an embodiment. FIG. 11 is a plan view of a fourth layer of a substrate used in the rotation sensor according to an embodiment. FIG. 12 is a circuit block diagram of the rotation sensor according to an embodiment. FIG. 13 is a graph showing changes in a detection signal of the rotation sensor according to an embodiment.

[0009] Rotation sensors according to embodiments will be described below with reference to the drawings. The figures described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components do not necessarily reflect the actual dimensional ratios. Furthermore, the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0010] (Embodiment) Hereinafter, a rotation sensor 1 according to an embodiment will be described with reference to Figs.

[0011] (1) Overview First, an overview of a rotation sensor 1 according to an embodiment will be described with reference to FIG.

[0012] Fig. 1 is a front view of a main part of a rotation sensor 1 according to an embodiment. As shown in Fig. 1, the rotation sensor 1 according to the embodiment is a sensor for detecting the rotation angle of a rotating object 4. The rotating object 4 is, for example, a rotating shaft (hereinafter also referred to as "rotating shaft 4") of an electric motor mounted on an electric vehicle (including two-wheeled vehicles), a hybrid vehicle (including two-wheeled vehicles), or industrial equipment (for example, a robot arm). The rotation sensor 1 is, for example, an inductive sensor. That is, the rotation sensor 1 can detect the rotation angle of a rotor 2 relative to a stator 3 (described below) by detecting changes in a magnetic field caused by eddy currents that accompany the rotation of a rotor 2 (described below).

[0013] Here, examples of sensors that detect the rotation angle of the rotating object 4 include sensors using magnetoresistive elements (MR sensors) and sensors using Hall elements. However, while these sensors can detect the rotation angle of a rotating object 4 with a rotation speed of approximately several thousand rpm, they may not be able to detect the rotation speed of a rotating object 4 with a rotation speed exceeding 10,000 rpm. On the other hand, an inductive sensor such as the rotation sensor 1 can detect the rotation speed of a rotating object 4 even if the rotation speed exceeds 10,000 rpm.

[0014] The rotation sensor 1 according to the embodiment employs the following configuration for the purpose of miniaturization.

[0015] 1, the rotation sensor 1 includes a rotor 2 and a stator 3. The rotor 2 is electrically conductive, is attached to a rotating object 4, and rotates integrally with the rotating object 4. The stator 3 faces the rotor 2 in one direction D1. That is, the one direction D1 is the direction in which the rotor 2 and the stator 3 face each other, for example, the up-and-down direction.

[0016] The stator 3 includes a substrate 31 , an excitation coil 32 , a detection coil 33 , electronic components 34 , a wiring pattern portion 35 , and a ground conductor 36 .

[0017] The substrate 31 has a facing surface 301 that faces the rotor 2 in one direction D1 and an opposite surface 304 that faces in the opposite direction from the facing surface 301. The facing surface 301 of the substrate 31 corresponds to the "first main surface of the substrate" in this disclosure. The opposite surface 304 of the substrate 31 corresponds to the "second main surface opposite to the first main surface of the substrate" in this disclosure. The excitation coil 32 is disposed on the facing surface 301 of the substrate 31 and generates a magnetic field. The detection coil 33 is disposed on the facing surface 301 of the substrate 31 and detects changes in the magnetic field. The electronic component 34 is disposed on the opposite surface 304 of the substrate 31.

[0018] The wiring pattern portion 35 is electrically connected to the electronic components 34. The ground conductor 36 is disposed between the rotor 2 and the wiring pattern portion 35 in the one direction D1. The ground conductor 36 is disposed on the opposing surface 301 of the substrate 31. The ground conductor 36 is a conductor set to the same potential as the ground of the circuit (see FIG. 12 ) of the rotation sensor 1 configured by the electronic components 34 and the wiring pattern portion 35. The circuit configuration and angle detection of the rotation sensor 1 will be described later.

[0019] In the rotation sensor 1 of this embodiment, the electronic components 34 and the wiring pattern portion 35 are arranged in a position overlapping with the rotor 2 in the direction D1 (see FIG. 1 ). As a result, even if the position of the rotor 2 fluctuates in the direction D1 while the rotation sensor 1 is in operation, the ground conductor 36 can suppress fluctuations in the impedance of the wiring pattern portion 35. This makes it possible to stabilize the operation of the circuit of the rotation sensor 1. Therefore, according to this embodiment, the rotation sensor 1 can be made smaller without reducing detection accuracy.

[0020] (2) Details Next, details of the rotation sensor 1 according to the embodiment will be described with reference to FIGS. 1 to 13. FIG. 4 is a plan view of the rotation sensor 1 according to the embodiment, seen through the surface of the rotor 2. Note that in FIG. 4, the rotor 2 is dot-hatched to easily distinguish the rotor 2 from the stator 3, and the dot-hatching in FIG. 4 does not show the cross section of the rotor 2. Also, in FIG. 4, the detector coil 33 is shown by a solid line on the facing surface 301 of the substrate 31. However, as will be described later, the detector coil 33 is disposed on both the first layer (facing surface 301) and the second layer 302 of the substrate 31. In other words, the detector coil 33 shown in FIG. 4 is a combination of a first detector coil pattern portion 33A (see FIG. 8) on the first layer (facing surface 301) of the substrate 31 and a second detector coil pattern portion 33B (see FIG. 9) on the second layer 302.

[0021] As described above, the rotation sensor 1 according to the embodiment is a sensor for detecting the rotation angle of a rotating object 4. As described above, the rotating object 4 is, for example, the rotating shaft 4 of an electric motor. As shown in FIGS. 1 to 4 , the rotation sensor 1 includes a rotor 2 (target) and a stator 3.

[0022] (2.1) Rotor The rotor 2 is made of a conductor (a material having electrical conductivity) such as a steel plate, and is attached to the rotating object 4 to rotate integrally with the rotating object 4. More specifically, the rotor 2 is attached to the tip of the rotating shaft 4 to rotate integrally with the rotating shaft 4.

[0023] 5 is a plan view of the rotor 2 used in the rotation sensor 1 according to the embodiment. As shown in FIGS. 4 and 5 , the rotor 2 has a rotor body 21 and a plurality of (four in the illustrated example) conductive portions 22.

[0024] The rotor body 21 has an annular shape in a plan view from one direction D1. As shown in FIG. 1 , the one direction D1 is the direction in which the rotor 2 and the stator 3 face each other. In other words, the one direction D1 is a direction along the rotation axis 4, which is the rotating object 4. The rotor body 21 has a through hole 211. The through hole 211 penetrates the rotor body 21 in the thickness direction of the rotor body 21 (the direction perpendicular to the paper surface of FIG. 5 ). The tip of the rotation shaft 4 is attached to the center of the rotor body 21 by fitting into the through hole 211 of the rotor body 21. The rotation shaft 4 has a circular shape in a plan view from one direction D1.

[0025] The multiple conductive portions 22 are arranged at equal intervals along the outer edge of the rotor body 21. That is, the multiple conductive portions 22 are arranged along the rotation direction DR1 of the rotor 2. Each conductive portion 22 protrudes in a direction away from the center of rotation RC1 of the rotor 2 when viewed from the outer edge of the rotor body 21. In this embodiment, the rotor 2 has four conductive portions 22, and two adjacent conductive portions 22 are shifted by 90 degrees from each other in the rotation direction DR1 of the rotor 2. In other words, the multiple conductive portions 22 extend radially from the center of rotation RC1 of the rotor 2. That is, the four conductive portions 22 extend radially from the center of rotation RC1 of the rotor 2 and are provided at equal intervals in the circumferential direction of the rotor body 21.

[0026] Each of the plurality of conductive portions 22 has a fan shape in a plan view from the one direction D1. In the rotor 2, a plurality of gaps 23 are provided so that the plurality of conductive portions 22 are spaced apart from one another. That is, in the rotor 2, the plurality of conductive portions 22 and the plurality of gaps 23 are alternately arranged along the rotation direction DR1 of the rotor 2. In this embodiment, the shape of each of the plurality of conductive portions 22 and the shape of each of the plurality of gaps 23 are substantially the same in a plan view from the one direction D1, but they may be different. Also, in this embodiment, the rotor main body 21 and the plurality of conductive portions 22 are integrated, but they may be separate bodies as long as they are electrically connected.

[0027] The center of rotation RC1 of the rotor 2 is the center of rotation of the rotor 2, and is the center of the through-hole 211 as shown in Figures 4 and 5. The radial direction of the rotor 2 centered on the center of rotation RC1 is referred to as the "radial direction R1." The rotor body 21 is disposed closer to the center of rotation RC1 in the radial direction R1 than the detection coil 33, and the conductive portion 22 is disposed opposite the detection coil 33 (see Figure 4).

[0028] Note that, like each conductive portion 22, when viewed from the outer edge of the rotor body 21, protruding in a direction away from the center of rotation RC1 of the rotor 2 is referred to as "protruding outward from the outer edge of the rotor body 21." Also, when, like the rotor body 2, it is positioned closer to the center of rotation RC1 in the radial direction R1 than the detection coil 33, it is referred to as "positioned more inward than the detection coil 33." Hereinafter, "inner" and "outer" will be defined in this manner.

[0029] The rotor 2 configured in this manner has a so-called end shaft structure, which is attached to the tip of the rotating shaft 4 and rotates integrally with the rotating shaft 4. The rotor 2 faces the stator 3 in one direction D1. More specifically, the rotor 2 faces the first main surface (opposing surface) of the substrate 31 in one direction D1.

[0030] 4 and 5, "P1" is the reference position (origin position) of the rotor 2 relative to the stator 3, and is a position where the rotation angle (mechanical angle) of the rotor 2 relative to the stator 3 is 0 degrees or 360 degrees. Also, in FIGS. 4 and 5, "P2" is a position where the rotation angle of the rotor 2 relative to the stator 3 is 90 degrees. Also, in FIGS. 4 and 5, "P3" is a position where the rotation angle of the rotor 2 relative to the stator 3 is 180 degrees. Also, in FIGS. 4 and 5, "P4" is a position where the rotation angle of the rotor 2 relative to the stator 3 is 270 degrees.

[0031] (2.2) Stator The stator 3 faces the rotor 2 attached to the rotating object 4 in one direction D1. As shown in FIG. 1 , the stator 3 includes a substrate 31, an excitation coil 32, a detection coil 33, electronic components 34, a wiring pattern portion 35, and a ground conductor 36.

[0032] In this embodiment, the electronic component 34 is disposed at a position overlapping the ground conductor 36 in the direction D1. The wiring pattern portion 35 is also disposed at a position overlapping the ground conductor 36 in the direction D1.

[0033] The substrate 31 is, for example, a printed wiring board made of glass epoxy resin. The substrate 31 has a circular shape when viewed from a plane in one direction D1 (see FIG. 4). The substrate 31 is arranged so that the center of the circle of the substrate 31 coincides with the rotation center RC1 of the rotor 2. A facing surface 301 of the substrate 31 faces the rotor 2 in the one direction D1. An excitation coil 32, a detection coil 33, and a ground conductor 36 are arranged on the facing surface 301 of the substrate 31. An electronic component 34 (described later) and a part of a wiring pattern portion 35 are arranged on an opposite surface 304 of the substrate 31 opposite the facing surface 301.

[0034] When an AC current output from an oscillator 362 (see FIG. 12 ) described below flows through the excitation coil 32, the excitation coil 32 generates an AC magnetic field that crosses the detection coil 33 along one direction D1. Here, the frequency of the AC current output from the oscillator 362 is, for example, 1 MHz to 10 MHz.

[0035] The detection coil 33 detects changes in the AC magnetic field generated by the excitation coil 32. As shown in FIG. 4 , the detection coil 33 includes a first detection coil 331 and a second detection coil 332. The first detection coil 331 and the second detection coil 332 are offset by 45 degrees from each other in the rotation direction DR1 of the rotor 2. As a result, the first detection coil 331 detects a first voltage signal corresponding to a first sine wave signal corresponding to the rotation angle of the rotor 2 relative to the stator 3. Furthermore, the second detection coil 332 detects a second voltage signal corresponding to a first cosine wave signal corresponding to the rotation angle of the rotor 2 relative to the stator 3.

[0036] (2.2.1) Multilayer Substrate: The substrate 31 is a multilayer substrate in this embodiment. More specifically, the substrate 31 is a four-layer substrate. FIG. 6 is a first cross-sectional view of the substrate 31 used in the rotation sensor 1 according to the embodiment. FIG. 7 is a second cross-sectional view of the substrate 31 used in the rotation sensor 1 according to the embodiment. Note that the cross-sectional views shown in FIGS. 6 and 7 are merely schematic drawings showing the arrangement and connection relationships of elements and wiring, and do not represent actual dimensions or scale. As shown in FIGS. 6 and 7 , the substrate 31 has multiple (two in the illustrated example) prepregs 311 and 312 and a core 313. The multiple prepregs 311 and 312 are positioned on both sides of the core 313 in one direction D1. Note that, hereinafter, a surface of a certain substrate (or a certain layer) facing an object is referred to as the "object-side surface of the substrate (or layer)," and a surface facing away from the object is referred to as the "opposite surface of the substrate (or layer) facing away from the object."

[0037] The surface of the prepreg 311 opposite the core 313 corresponds to the opposing surface 301 of the substrate 31, and in this embodiment, this is also referred to as the "first layer 301" of the substrate 31. The surface of the core 313 facing the prepreg 311 is the "second layer 302" of the substrate 31 in this embodiment. The second layer 302 of the substrate 31 corresponds to the "layer closest to the first main surface" in this disclosure. The surface of the core 313 facing the prepreg 312 is the "third layer 303" of the substrate 31 in this embodiment. The surface of the prepreg 312 opposite the core 313 corresponds to the opposing surface 304 of the substrate 31, and in this embodiment, this is also referred to as the "fourth layer 304" of the substrate 31.

[0038] In this embodiment, the excitation coil 32 includes a first excitation coil pattern portion 32A and a second excitation coil pattern portion 32B (see FIG. 6 ). The first excitation coil pattern portion 32A is disposed on a first layer 301 of the substrate 31. The second excitation coil pattern portion 32B is disposed on a second layer 302 of the substrate 31.

[0039] In this embodiment, the detection coil 33 includes a first detection coil pattern portion 33A and a second detection coil pattern portion 33B (see FIG. 6 ). The first detection coil pattern portion 33A is disposed on a first layer 301 of the substrate 31. The second detection coil pattern portion 33B is disposed on a second layer 302 of the substrate 31.

[0040] In this embodiment, the ground conductor 36 includes a first ground conductor pattern portion 36A, a second ground conductor pattern portion 36B, a third ground conductor pattern portion 36C, and a fourth ground conductor pattern portion 36D (see FIG. 7 ). The first ground conductor pattern portion 36A is arranged on a first layer 301 of the substrate 31. The second ground conductor pattern portion 36B is arranged on a second layer 302 of the substrate 31. The third ground conductor pattern portion 36C is arranged on a third layer 303 of the substrate 31. The fourth ground conductor pattern portion 36D is arranged on a fourth layer (opposite surface 304) of the substrate 31.

[0041] 6 and 7, the substrate 31 is provided with a plurality of vias 314 and a plurality of through holes 316. The plurality of vias 314 include a first via 314a, a second via 314b, a third via 314c, a fourth via 314d, a fifth via 314e, a sixth via 314f, a seventh via 314g, an eighth via 314h, a ninth via 314i, and a tenth via 314j. Each of the first via 314a to the tenth via 314j penetrates the two prepregs 311 and 312 and the core 313. In FIGS. 6 and 7, the portions of the first via 314a to the seventh via 314j that are electrically connected to the respective layers are indicated by solid lines, and the vias that are not electrically connected to the respective layers are indicated by dotted lines.

[0042] The first via 314a electrically connects the first layer 301 and the second layer 302 (see FIG. 6 ). The second via 314b electrically connects the first layer 301 and the second layer 302 (see FIG. 6 ). More specifically, the first via 314a electrically connects the first excitation coil pattern portion 32A of the excitation coil 32 arranged on the first layer 301 of the substrate 31 to the second excitation coil pattern portion 32B of the excitation coil 32 arranged on the second layer 302 of the substrate 31. The second via 314b electrically connects the first detector coil pattern portion 33A of the detector coil 33 arranged on the first layer 301 of the substrate 31 to the second detector coil pattern portion 33B of the detector coil 33 arranged on the second layer 302 of the substrate 31.

[0043] The third via 314c electrically connects the second layer 302 and the third layer 303 (see FIG. 6 ). The fourth via 314d electrically connects the second layer 302 and the third layer 303 (see FIG. 6 ). More specifically, the third via 314c electrically connects the second excitation coil pattern portion 32B of the excitation coil 32 arranged on the second layer 302 of the substrate 31 to a part of the wiring pattern portion 35 arranged on the third layer 303 of the substrate 31. The fourth via 314d electrically connects the second detection coil pattern portion 33B of the detection coil 33 arranged on the second layer 302 of the substrate 31 to a part of the wiring pattern portion 35 arranged on the third layer 303 of the substrate 31.

[0044] The fifth via 314e electrically connects the third layer 303 and the fourth layer 304 (see FIG. 6 ). The sixth via 314f electrically connects the third layer 303 and the fourth layer 304 (see FIG. 6 ). More specifically, the fifth via 314e electrically connects a portion of the wiring pattern portion 35 arranged on the third layer 303 of the substrate 31 to the electronic component 34 arranged on the fourth layer 304 of the substrate 31. The sixth via 314f electrically connects a portion of the wiring pattern portion 35 arranged on the third layer 303 of the substrate 31 to the electronic component 34 arranged on the fourth layer 304 of the substrate 31.

[0045] The seventh via 314g electrically connects the second layer 302 and the fourth layer 304 (see FIG. 6 ). More specifically, the seventh via 314g electrically connects the second detection coil pattern portion 33B arranged on the second layer 302 of the substrate 31 to a part of the wiring pattern portion 35 arranged on the fourth layer 304.

[0046] The eighth via 314h, the ninth via 314i, and the tenth via 314j electrically connect all layers (i.e., the first layer 301 to the fourth layer 304) (see FIGS. 6 and 7). More specifically, the eighth via 314h electrically connects the first excitation coil pattern portion 32A of the excitation coil 32 arranged on the first layer 301 of the substrate 31 to a part of the wiring pattern portion 35 arranged on the fourth layer 304. Furthermore, the ninth via 314i electrically connects the first detection coil pattern portion 33A of the detection coil 33 arranged on the first layer 301 of the substrate 31 to a part of the wiring pattern portion 35 arranged on the fourth layer 304. The tenth via 314j electrically connects the first ground conductor pattern portion 36A on the first layer 301, the second ground conductor pattern portion 36B on the second layer 302, the third ground conductor pattern portion 36C on the third layer 303, and the fourth ground conductor pattern portion 36D on the fourth layer 304.

[0047] The through holes 316 penetrate the two prepregs 311 and 312, the core 313, and all the layers (i.e., the first layer 301 to the fourth layer 304) (see FIG. 7 ). The through holes 316 shown in FIG. 7 correspond to first through holes 316a (see FIGS. 8 to 11 ) described later. More specifically, the first through holes 316a electrically connect the first ground conductor pattern 36A on the first layer 301, the second ground conductor pattern 36B on the second layer 302, the third ground conductor pattern 36C on the third layer 303, and the fourth ground conductor pattern 36D on the fourth layer 304.

[0048] (2.2.2) First Layer FIG. 8 is a plan view showing the first layer 301 of the substrate 31. As shown in FIG. 8, the first layer 301 of the substrate 31 is provided with a first excitation coil pattern portion 32A of the excitation coil 32, a first detection coil pattern portion 33A of the detection coil 33, and a first ground conductor pattern portion 36A of the ground conductor 36. Note that the countless white circles on the first layer 301 in FIG. 8 correspond to vias 314 for electrical connection with other layers (see FIGS. 6 and 7). Also, as shown in FIG. 8, an X-axis and a Y-axis are defined that are orthogonal to each other on a plane parallel to the opposing surface 301 (first layer) of the substrate 31.

[0049] The first excitation coil pattern portion 32A of the excitation coil 32 is arranged in an annular shape on the first layer 301 of the substrate 31 (see FIG. 8 ). More specifically, the first excitation coil pattern portion 32A of the excitation coil 32 is arranged in an annular shape on the first layer 301 of the substrate 31 so as to follow the outer edge 20 of the rotor 2 in a plan view from one direction D1. Here, the "outer edge 20 of the rotor 2" is a circumference that includes the arc-shaped outer edge 221 of each of the multiple conductive portions 22 that follows the rotation direction DR1 of the rotor 2, as shown in FIGS. 4 and 5 . The first excitation coil pattern portions 32A are arranged concentrically so as to overlap in the radial direction R1 of the substrate 31.

[0050] The first end 32Ao (outside) of the first excitation coil pattern portion 32A is electrically connected to the second excitation coil pattern portion 32B of the excitation coil 32 arranged on the second layer 302 of the substrate 31 by a first via 314a (see FIG. 6). The second end 32Ai (inside) of the first excitation coil pattern portion 32A of the excitation coil 32 is electrically connected to a part of the wiring pattern portion 35 arranged on the fourth layer 304 by an eighth via 314h (see FIG. 6).

[0051] The first detector coil pattern portion 33A of the detector coil 33 is disposed inside the first excitation coil pattern portion 32A of the excitation coil 32 on the first layer 301 of the substrate 31 (see FIG. 8 ). More specifically, the first detector coil pattern portion 33A is disposed inside the first excitation coil pattern portion 32A and outside the first ground conductor pattern portion 36A on the first layer (opposing surface 301) of the substrate 31. The first detector coil pattern portion 33A is disposed in a wavy, spiral pattern. The first detector coil pattern portion 33A is disposed in the rotation direction DR1. The first detector coil pattern portion 33A includes a portion of the first detector coil 331 and a portion of the second detector coil 332. The first detector coil pattern portion 33A is electrically connected to the second detector coil pattern portion 33B of the detector coil 33 formed on the second layer 302 of the substrate 31 by a second via 314b (see FIG. 6 ).

[0052] The first ground conductor pattern portion 36A of the ground conductor 36 is disposed inside the first detection coil pattern portion 33A of the detection coil 33 on the first layer 301 of the substrate 31 (see FIG. 8 ). More specifically, the first ground conductor pattern portion 36A includes a solid conductor. In the present disclosure, a "solid conductor" refers to a conductor having a region extending along a first axis and a region extending along a second axis in a plane defined by two orthogonal axes (a Cartesian coordinate system). Therefore, a solid conductor is typically rectangular in plan view from the direction D1 on the plane, but may also be polygonal. In this embodiment, when Cartesian coordinates are defined on the plane of the first layer 301 of the substrate 31, the solid conductor has a region extending along the X-axis and a region extending along the Y-axis near the center RC1 of the plane. More specifically, the solid conductor is circular in plan view from the direction D1 on the plane of the first layer 301 of the substrate 31.

[0053] The through holes 316 are provided in the first layer 301 of the substrate 31. The through holes 316 are surrounded by the solid conductor of the first ground conductor pattern portion 36A. The through holes 316 include a first through hole 316a, a second through hole 316b, a third through hole 316c, a fourth through hole 316d, a fifth through hole 316e, and a sixth through hole 316f.

[0054] The first through-hole 316a is connected to the ground terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1. The first through-hole 316a is electrically connected to the first ground conductor pattern portion 36A on the first layer 301, the second ground conductor pattern portion 36B on the second layer 302, the third ground conductor pattern portion 36C on the third layer 303, and the fourth ground conductor pattern portion 36D on the fourth layer 304 (see FIG. 7). The second through-hole 316b, the third through-hole 316c, the fourth through-hole 316d, the fifth through-hole 316e, and the sixth through-hole 316f are connected to the power supply terminal 37 and the input / output terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1.

[0055] (2.2.3) Second Layer Figure 9 is a plan view showing the second layer 302 of the substrate 31. As shown in Figure 9, the second layer 302 of the substrate 31 is provided with a second excitation coil pattern portion 32B of the excitation coil 32, a second detection coil pattern portion 33B of the detection coil 33, and a second ground conductor pattern portion 36B of the ground conductor 36. Note that the countless white circles on the second layer 302 in Figure 9 correspond to vias 314 for electrical connection with other layers (see Figures 6 and 7). Also, as shown in Figure 9, an X-axis and a Y-axis are defined that are orthogonal to each other on a plane parallel to the second layer 302 of the substrate 31.

[0056] The second excitation coil pattern portion 32B of the excitation coil 32 is arranged in an annular shape on the second layer 302 of the substrate 31 (see FIG. 9 ). More specifically, the second excitation coil pattern portion 32B is arranged in an annular shape on the opposing surface 301 of the substrate 31 so as to follow the outer edge 20 of the rotor 2 in a plan view from one direction D1. The second excitation coil pattern portions 32B are arranged in concentric circles so as to overlap in the radial direction R1 of the substrate 31.

[0057] A first end 32Bo (outside) of the second excitation coil pattern portion 32B is electrically connected to the first excitation coil pattern portion 32A of the excitation coil 32 formed on the first layer (opposing surface 301) of the substrate 31 by a first via 314a (see FIG. 6). A second end 32Bi (inside) of the second excitation coil pattern portion 32B is electrically connected to a part of the wiring pattern portion 35 formed on the third layer 303 by a third via 314c (see FIG. 6).

[0058] The second detector coil pattern portion 33B of the detector coil 33 is disposed inside the second excitation coil pattern portion 32B of the excitation coil 32 on the second layer 302 of the substrate 31 (see FIG. 9 ). More specifically, the second detector coil pattern portion 33B is disposed inside the second excitation coil pattern portion 32B and outside the second ground conductor pattern portion 36B on the second layer 302 of the substrate 31. The second detector coil pattern portion 33B is disposed in a wavy, spiral pattern. The second detector coil pattern portion 33B of the detector coil 33 includes a remaining portion of the first detector coil 331 described above excluding a portion thereof and a remaining portion of the second detector coil 332 described above excluding a portion thereof.

[0059] The second detector coil pattern portion 33B is electrically connected to the first detector coil pattern portion 33A of the detector coil 33 arranged on the first layer 301 of the substrate 31 by a second via 314b (see FIG. 6). The second detector coil pattern portion 33B is also electrically connected to a part of the wiring pattern portion 35 arranged on the third layer 303 of the substrate 31 by a fourth via 314d. The second detector coil pattern portion 33B is also electrically connected to a part of the wiring pattern portion 35 arranged on the fourth layer 304 of the substrate 31 by a seventh via 314g.

[0060] The second ground conductor pattern portion 36B of the ground conductor 36 is disposed inside the second detection coil pattern portion 33B of the detection coil 33 on the second layer 302 of the substrate 31 (see FIG. 9 ). The second ground conductor pattern portion 36B includes a solid conductor. In this embodiment, when Cartesian coordinates are defined on the plane of the second layer 302 of the substrate 31, the solid conductor extends in the direction along the X-axis near the center RC1 of the plane and has a region extending in the direction along the Y-axis. More specifically, the solid conductor has a circular shape when viewed from one direction D1 on the plane of the second layer 302 of the substrate 31.

[0061] The second ground conductor pattern portion 36B arranged on the second layer 302 of the substrate 31 is arranged at a position overlapping in the one direction D1 with the first ground conductor pattern portion 36A arranged on the first layer 301 of the substrate 31. In this embodiment, the circular outline of the first ground conductor pattern portion 36A overlaps in the one direction D1 with the circular outline of the second ground conductor pattern portion 36B.

[0062] Through holes 316 are provided in the second layer 302 of the substrate 31. The through holes 316 are surrounded by the solid conductor of the second ground conductor pattern portion 36B. The through holes 316 include a first through hole 316a, a second through hole 316b, a third through hole 316c, a fourth through hole 316d, a fifth through hole 316e, and a sixth through hole 316f.

[0063] The first through-hole 316a is connected to the ground terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1. The first through-hole 316a is electrically connected to the first ground conductor pattern portion 36A on the first layer 301, the second ground conductor pattern portion 36B on the second layer 302, the third ground conductor pattern portion 36C on the third layer 303, and the fourth ground conductor pattern portion 36D on the fourth layer 304 (see FIG. 7). The second through-hole 316b, the third through-hole 316c, the fourth through-hole 316d, the fifth through-hole 316e, and the sixth through-hole 316f are connected to the power supply terminal 37 and the input / output terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1.

[0064] (2.2.4) Third Layer FIG. 10 is a plan view showing the third layer 303 of the substrate 31. As shown in FIG. 10 , the third ground conductor pattern portion 36C of the ground conductor 36 and part of the wiring pattern portion 35 are arranged on the third layer 303 of the substrate 31. Note that the countless white circles on the third layer 303 in FIG. 10 correspond to vias 314 for electrical connection with other layers (see FIGS. 6 and 7 ). Also, as shown in FIG. 10 , an X-axis and a Y-axis are defined that are orthogonal to each other on a plane parallel to the third layer 303 of the substrate 31.

[0065] The third ground conductor pattern portion 36C of the ground conductor 36 is disposed near the center of the third layer 303 of the substrate 31 (see FIG. 10 ). The third ground conductor pattern portion 36C includes a solid conductor. In this embodiment, when Cartesian coordinates are defined on the plane of the third layer 303 of the substrate 31, the solid conductor has a region that extends along the X-axis near the center RC1 of the plane and also extends along the Y-axis. More specifically, the solid conductor has a circular shape when viewed from one direction D1 on the plane of the third layer 303 of the substrate 31.

[0066] The third ground conductor pattern portion 36C on the third layer 303 is disposed at a position overlapping in the direction D1 with the first ground conductor pattern portion 36A on the first layer 301 and the second ground conductor pattern portion 36B on the second layer 302. In this embodiment, the circular outline of the first ground conductor pattern portion 36A, the circular outline of the second ground conductor pattern portion 36B, and the circular outline of the third ground conductor pattern portion 36C overlap in the direction D1.

[0067] Through holes 316 are provided in the third layer 303 of the substrate 31. The through holes 316 are surrounded by the solid conductor of the third ground conductor pattern portion 36C. The through holes 316 include a first through hole 316a, a second through hole 316b, a third through hole 316c, a fourth through hole 316d, a fifth through hole 316e, and a sixth through hole 316f.

[0068] The first through-hole 316a is connected to the ground terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1. The first through-hole 316a is electrically connected to the first ground conductor pattern portion 36A on the first layer 301, the second ground conductor pattern portion 36B on the second layer 302, the third ground conductor pattern portion 36C on the third layer 303, and the fourth ground conductor pattern portion 36D on the fourth layer 304 (see FIG. 7). The second through-hole 316b, the third through-hole 316c, the fourth through-hole 316d, the fifth through-hole 316e, and the sixth through-hole 316f are connected to the power supply terminal 37 and the input / output terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1.

[0069] A portion of the wiring pattern portion 35 includes a first wiring pattern portion 351 and a second wiring pattern portion 352 on the third layer 303 of the substrate 31 .

[0070] The first wiring pattern portion 351 of the wiring pattern portion 35 electrically connects the electronic component 34 and the excitation coil 32. More specifically, the first wiring pattern portion 351 extends outward in the radial direction R1 from near the center RC1 of the third layer 303 of the substrate 31, crossing the edge of the area of ​​the third ground conductor pattern portion 36C (see FIG. 10 ). The first wiring pattern portion 351 curves in the rotational direction DR1 outside the area of ​​the third ground conductor pattern portion 36C. Note that although the first wiring pattern portion 351 overlaps a portion of the third ground conductor pattern portion 36C, the first wiring pattern portion 351 and the third ground conductor pattern portion 36C are not electrically connected.

[0071] A first end 351i (center side) of the first wiring pattern portion 351 of the wiring pattern portion 35 is electrically connected to the electronic component 34 arranged on the fourth layer 304 of the substrate 31 by a fifth via 314e (see FIG. 6). Also, a second end 351o (outside) of the first wiring pattern portion 351 of the wiring pattern portion 35 is electrically connected to the second excitation coil pattern portion 32B of the excitation coil 32 formed on the second layer 302 of the substrate 31 by a third via 314c (see FIG. 6).

[0072] The second wiring pattern 352 electrically connects the electronic component 34 and the detection coil 33. More specifically, the second wiring pattern 352 extends from the inside to the outside so as to cross the edge of the area of ​​the third ground conductor pattern 36C on the third layer 303 (see FIG. 10 ). Note that although the second wiring pattern 352 overlaps a part of the third ground conductor pattern 36C, the second wiring pattern 352 and the third ground conductor pattern 36C are not electrically connected.

[0073] A first end 352i (inside) of the second wiring pattern portion 352 of the wiring pattern portion 35 is electrically connected to a part of the wiring pattern portion 35 arranged on the fourth layer (opposite surface 304) of the substrate 31 by a sixth via 316f (see FIG. 6). Also, a second end 352o (outside) of the second wiring pattern portion 352 of the wiring pattern portion 35 is electrically connected to the second detection coil pattern portion 33B of the detection coil 33 formed on the second layer 302 of the substrate 31 by a fourth via 314d (see FIG. 6).

[0074] (2.2.5) Fourth Layer Figure 11 is a plan view showing the fourth layer 304 of the substrate 31. As shown in Figure 11, the fourth layer (opposite surface 304) of the substrate 31 is provided with electronic components 34, part of the wiring pattern portion 35, and a fourth ground conductor pattern portion 36D of the ground conductor 36. Note that the countless white circles on the fourth layer 304 in Figure 11 correspond to vias 314 for electrical connection with other layers (see Figures 6 and 7). Also, as shown in Figure 11, an X-axis and a Y-axis are defined that are orthogonal to each other on a plane parallel to the fourth layer 304 of the substrate 31.

[0075] In this embodiment, the electronic components 34 are composed of one IC component 34a and eleven chip components 34b (see FIG. 11). The IC component 34a is rectangular in plan view from one direction D1. The chip components 34b are chip capacitors. The electronic components 34 and the wiring pattern portion 35 connected to the electronic components 34 form a circuit block of the rotation sensor 1, and the circuit block will be described in detail later.

[0076] A portion of the wiring pattern portion 35 includes a first wiring pattern portion 351 , a second wiring pattern portion 352 , and a third wiring pattern portion 353 on the fourth layer 304 of the substrate 31 .

[0077] The first wiring pattern portion 351 electrically connects the electronic component 34 and the excitation coil 32. More specifically, the first wiring pattern portion 351 extends from near the electronic component 34 outward in the radial direction R1 and curves in the rotational direction DR1 (see FIG. 11 ). A first end (inner side) of the first wiring pattern portion 351 is bifurcated, one end electrically connected to the rectangular IC component 34a and the other end electrically connected to the chip component 34b. A second end (outer side) of the first wiring pattern portion 351 is electrically connected to the first excitation coil pattern portion 32A of the excitation coil 32 arranged on the first layer 301 of the substrate 31 by an eighth via 314h (see FIG. 6 ).

[0078] The second wiring pattern portion 352 electrically connects the electronic component 34 and the detection coil 33. More specifically, the second wiring pattern portion 352 includes a first portion 352a, a second portion 352b, and a third portion 352c. The first portion 352a, the second portion 352b, and the third portion 352c extend from near the electronic component 34 outward in the radial direction R1.

[0079] A first end (inside) of the first portion 352a of the second wiring pattern portion 352 is connected to the chip component 34b of the electronic component 34. A second end (outside) of the first portion 352a of the second wiring pattern portion 352 is electrically connected to the first detection coil pattern portion 33A of the detection coil 33 on the first layer 301 of the substrate 31 by a ninth via 314i (see FIG. 6).

[0080] A first end (inside) of the second portion 352b of the second wiring pattern portion 352 is connected to the chip component 34b of the electronic component 34. A second end (outside) of the second portion 352b of the second wiring pattern portion 352 is electrically connected to the first detection coil pattern portion 33A of the detection coil 33 on the first layer 301 of the substrate 31 by a ninth via 314i (see FIG. 6).

[0081] A first end (inside) of the third portion 352c of the second wiring pattern portion 352 is connected to the chip component 34b of the electronic component 34. A second end (outside) of the third portion 352c of the second wiring pattern portion 352 is electrically connected to the second detection coil pattern portion 33B of the detection coil 33 on the second layer 302 of the substrate 31 by a seventh via 314g (see FIG. 6).

[0082] The third wiring pattern portion 353 electrically connects the electronic component 34 to another electronic component 34. The third wiring pattern portion 353 includes a first portion 353a and a second portion 353b. More specifically, the first portion 353a electrically connects the IC component 34a to the chip component 34b (see FIG. 11 ). Alternatively, the second portion 353b electrically connects the chip component 34b to the chip component 34b (see FIG. 11 ).

[0083] As described above, in this embodiment, the first wiring pattern portion 351 , the second wiring pattern portion 352 , and the third wiring pattern portion 353 are arranged on the opposite surface 304 (fourth layer) of the substrate 31 .

[0084] The fourth ground conductor pattern portion 36D of the ground conductor 36 has a substantially circular shape in plan view from the one direction D1 and is disposed so as to surround the electronic components 34 and the wiring pattern portion 35 (see FIG. 11 ). The circular outline of the fourth ground conductor pattern portion 36D (see FIG. 11 ) overlaps, in the one direction D1, with the circular outline of the solid conductor of the third ground conductor pattern portion 36C on the third layer 303 of the substrate 31 (see FIG. 10 ). That is, in plan view from the one direction D1, the area of ​​the electronic components 34 and the wiring pattern portion 35 on the fourth layer 304 of the substrate 31 (see FIG. 11 ) is smaller than the area of ​​the solid conductor of the third ground conductor pattern portion 36C (see FIG. 10 ).

[0085] The through holes 316 are provided in the fourth layer 304 of the substrate 31. The through holes 316 are surrounded by a fourth ground conductor pattern portion 36D of the ground conductor 36. The through holes 316 include a first through hole 316a, a second through hole 316b, a third through hole 316c, a fourth through hole 316d, a fifth through hole 316e, and a sixth through hole 316f.

[0086] The first through-hole 316a is connected to the ground terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1. The first through-hole 316a is electrically connected to the first ground conductor pattern portion 36A on the first layer 301, the second ground conductor pattern portion 36B on the second layer 302, the third ground conductor pattern portion 36C on the third layer 303, and the fourth ground conductor pattern portion 36D on the fourth layer 304 (see FIG. 7). The second through-hole 316b, the third through-hole 316c, the fourth through-hole 316d, the fifth through-hole 316e, and the sixth through-hole 316f are connected to the power supply terminal 37 and the input / output terminal 37 (see FIG. 3) of the circuit (see FIG. 12) of the rotation sensor 1.

[0087] (2.3) Sensor Body The rotation sensor 1 further includes a sensor body 300. Fig. 2 is a perspective view showing the appearance of the rotation sensor 1 according to the embodiment. Fig. 3 is an exploded perspective view of the rotation sensor 1 according to the embodiment. As shown in Figs. 2 and 3, the sensor body 300 further includes a body 321, a cover member 322, an O-ring 323, and two mounting members 324.

[0088] The main body 321 has a housing portion 321a and two mounting arms 321b. The housing portion 321a houses the substrate 31. The housing portion 321a has a cylindrical shape with a circular opening at the top. The bottom of the housing portion 321a is circular in plan view. The substrate 31 is placed on the bottom of the housing portion 321a. The opening of the housing portion 321a is closed by a disk-shaped lid member 322. Six through holes 321c are formed in the bottom of the housing portion 321a. With the substrate 31 placed on the bottom of the housing portion 321a, six terminals 37 protruding from the substrate 31 (opposite surface 304) are inserted into the six through holes 321c. The six terminals 37 consist of a ground terminal, a power terminal, and four input / output terminals for the circuit of the rotation sensor 1. The circuit of the rotation sensor 1 is connected to the outside via the input / output terminals. Data detected by the circuit of the rotation sensor 1 is transmitted to the outside.

[0089] The O-ring 323 is an annular sealing member that ensures airtightness of the main body 321 and is disposed around the housing 321a. The two mounting arms 321b are connected to either side of the housing 321a. Each of the two mounting arms 321b has a through-hole 321d that penetrates in one direction D1. Two mounting members 324 fit into the two through-holes 321d. Using the two mounting members 324, the rotation sensor 1 can be mounted, as described above, inside an electric vehicle, a hybrid vehicle, or industrial equipment, for example.

[0090] (2.4) Circuit Configuration Next, the circuit configuration of the rotation sensor 1 will be described with reference to FIG.

[0091] Fig. 12 is a circuit block diagram of the rotation sensor 1 according to the embodiment. As shown in Fig. 12, the rotation sensor 1 includes an analog front-end circuit 361, an oscillator 362, two buffers 364 and 366, two inverters 365 and 367, a phase shifter 368, and a microcontroller 369. The analog front-end circuit 361, the oscillator 362, the multiple buffers 364 and 366, the multiple inverters 365 and 367, the phase shifter 368, and the microcontroller 369 are configured using electronic components 34 and a wiring pattern section 35 (see Fig. 11).

[0092] The analog front-end circuit 361 receives the first voltage signal from the first detection coil 331 and the second voltage signal from the second detection coil 332, demodulates the first voltage signal into a first sine wave signal, and demodulates the second voltage signal into a first cosine wave signal. The analog front-end circuit 361 also adjusts the gain of each of the first sine wave signal and the first cosine wave signal.

[0093] The oscillator 362 outputs, for example, an AC current of 1 to 10 MHz to the excitation coil 32. A capacitor 333 is connected between both ends of the excitation coil 32. When the AC current from the oscillator 362 flows in the excitation coil 32, the excitation coil 32 generates an AC magnetic field that penetrates the excitation coil 32 along one direction D1.

[0094] The buffer 364 outputs the first sine wave signal from the analog front-end circuit 361. The inverter 365 outputs a second sine wave signal obtained by inverting the phase of the first sine wave signal from the analog front-end circuit 361. The buffer 366 outputs the first cosine wave signal from the analog front-end circuit 361. The inverter 367 outputs a second cosine wave signal obtained by inverting the phase of the first cosine wave signal from the analog front-end circuit 361.

[0095] The phase shifter 368 detects the phase of each of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal input through the plurality of buffers 364 and 366 and the plurality of inverters 365 and 367 .

[0096] The microcontroller 369 has a memory. The microcontroller 369 executes a program stored in the memory to perform angle detection, which will be described later. In angle detection, the microcontroller 369 detects (calculates) the rotation angle (absolute angle) of the rotor 2 based on the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal. Note that angle detection will be described in the section "(3) Angle Detection" below.

[0097] (3) Angle Detection Next, angle detection executed by the microcontroller 369 will be described with reference to FIG.

[0098] Fig. 13 is a graph showing changes in the detection signal of the rotation sensor 1 according to this embodiment. In the rotation sensor 1, the first sine wave signal detected by the first detection coil 331 includes four periods of a sine wave per one rotation of the rotor 2, as indicated by the solid line a1 in Fig. 13 . In addition, in the rotation sensor 1, the first cosine wave signal detected by the second detection coil 332 includes four periods of a sine wave per one rotation of the rotor 2, as indicated by the dashed-dotted line a2 in Fig. 13 . Note that in Fig. 13 , the dashed line a3 indicates changes in the rotation angle (mechanical angle) of the rotor 2 corresponding to the first cosine wave signal, and the two-dot chain line a4 indicates changes in the rotation angle of the rotor 2 corresponding to the first sine wave signal.

[0099] As described above, the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal are input to the microcontroller 369. Therefore, the microcontroller 369 detects the rotation angle (absolute angle) of the rotor 2 based on the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal. The data detected by the microcontroller 369 is transmitted to the outside via the aforementioned input / output terminal 37 (see FIG. 3 ).

[0100] (4) Advantages: To reduce the size of the rotation sensor, a rotation sensor is considered as a comparative example in which a rotor attached to the tip of the rotating shaft faces the board in one direction (end shaft structure), and electronic components are placed on the surface of the board opposite to the facing surface.

[0101] However, in the rotation sensor of the comparative example, when the rotor position fluctuates in one direction (for example, up and down), the parasitic capacitance generated between the rotor and the wiring pattern of the electronic components fluctuates, causing the impedance of the wiring pattern to fluctuate. As a result, the operation of the detection circuit in the rotation sensor of the comparative example becomes unstable, and the detection accuracy decreases.

[0102] In contrast, in the rotation sensor 1 of this embodiment, in the end shaft structure as described above, the electronic components 34 are arranged on the opposite surface 304 of the substrate 31, and the ground conductor 36 is arranged between the rotor 2 and the wiring pattern portion 35 in the one direction D1 (see FIG. 1 ). As a result, even if the position of the rotor 2 fluctuates in the one direction D1 during operation of the rotation sensor 1, the ground conductor 36 can suppress fluctuations in the impedance of the wiring pattern portion 35. This makes it possible to stabilize the operation of the circuit of the rotation sensor 1 (see FIG. 12 ). Therefore, according to this embodiment, the rotation sensor 1 can be made smaller without reducing detection accuracy compared to the rotation sensor of the comparative example.

[0103] Furthermore, in the rotation sensor 1 of this embodiment, the wiring pattern portion 35 is arranged on the opposite surface 304 of the substrate 31, and the ground conductor 36 is arranged on the opposing surface 301 of the substrate 31 (see FIG. 1 ). This makes it difficult for the impedance of the wiring pattern portion 35 arranged on the opposite surface 304 of the substrate 31 to fluctuate. Therefore, the rotation sensor 1 can be made smaller without reducing detection accuracy.

[0104] Furthermore, in the rotation sensor 1 of this embodiment, the wiring pattern portion 35 is disposed at a position overlapping the ground conductor 36 in the direction D1 (see FIG. 1 ). This makes it difficult for the impedance of the wiring pattern portion 35 to fluctuate. Therefore, the rotation sensor 1 can be made smaller without reducing detection accuracy.

[0105] Furthermore, in the rotation sensor 1 of this embodiment, the ground conductor 36 includes a solid conductor (see FIGS. 8 to 10). At least a portion of the wiring pattern portion 35 is disposed on the fourth layer (opposite surface 304) of the substrate 31. In a plan view from one direction D1, the area of ​​at least a portion of the wiring pattern portion 35, including the electronic components 34 and the wiring pattern portion 35 on the fourth layer (opposite surface 304) of the substrate 31 (see FIG. 11), is smaller than the area of ​​the solid conductor of the ground conductor 36 (see FIGS. 8 to 10). This makes it less likely for the impedance of the wiring pattern portion 35 to fluctuate. Therefore, the rotation sensor 1 can be miniaturized without reducing detection accuracy.

[0106] Furthermore, in the rotation sensor 1 of this embodiment, the ground conductor 36 is arranged on the first layer 301, the second layer 302, and the third layer 303 of the substrate 31. This makes it difficult for the impedance of the wiring pattern portion 35 arranged on the fourth layer 304 of the substrate 31 to fluctuate. Therefore, the rotation sensor 1 can be made smaller without reducing detection accuracy.

[0107] (5) Modifications The above embodiment is merely one of various embodiments of the present disclosure. The above embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the above embodiment are listed below. The modifications described below can be applied in appropriate combinations.

[0108] In the above embodiment, the substrate 31 is described as a multilayer substrate (four-layer substrate), but the number of layers of the substrate 31 can be changed as appropriate. The number of layers of the substrate 31 may be six, eight, or ten or more layers. The substrate 31 may also be a double-sided substrate.

[0109] In the above embodiment, the ground conductor 36 includes a first ground conductor pattern portion 36A on the first layer 301, a second ground conductor pattern portion 36B on the second layer 302, and a third ground conductor pattern portion 36C on the third layer 303. The ground conductor 36 does not have to be arranged on all layers. The ground conductor 36 may be arranged on at least one of the first layer 301, the second layer 302, and the third layer 303. That is, if the substrate 31 is a multilayer substrate, the ground conductor 36 may be arranged on the first layer (opposing surface 301) of the substrate 31 and at least one of the multiple layers. Alternatively, if the substrate 31 is a double-sided substrate, the ground conductor 36 may be arranged only on the opposing surface 301 of the substrate 31. Even with this modification, the impedance of the wiring pattern portion 35 arranged on the opposing surface 304 of the substrate 31 can be made less likely to fluctuate. Therefore, the rotation sensor 1 can be miniaturized without reducing detection accuracy.

[0110] In the above embodiment, the electronic component 34 is disposed on the opposite surface 304 of the substrate 31, but the electronic component 34 may be, for example, an IC chip or chip component that is internally mounted (built-in) on the opposite surface 304 of the substrate 31. The electronic component 34 may also include a resistor, a coil, and a capacitor that are formed in a pattern on the opposite surface 304 of the substrate 31.

[0111] In the above embodiment, the electronic component 34 is composed of one IC component 34a and eleven chip components 34b, but the configuration of the electronic component 34 can be changed as appropriate as long as it has the functions of the circuit of the rotation sensor 1 (see Figure 12).

[0112] In this embodiment, the first wiring pattern portion 351, the second wiring pattern portion 352, and the third wiring pattern portion 353 are arranged on the opposite surface 304 of the substrate 31 (see FIG. 11 ). At least one of the first wiring pattern portion 351, the second wiring pattern portion 352, and the third wiring pattern portion 353 may be arranged on the opposite surface 304 of the substrate 31.

[0113] In the above embodiment, the excitation coil 32 includes a first excitation coil pattern portion 32A on the first layer 301 of the substrate 31 and a second excitation coil pattern portion 32B on the second layer 302 of the substrate 31, but the excitation coil 32 may be arranged only on the opposing surface 301 of the substrate 31.

[0114] The shape of the excitation coil 32 (first excitation coil pattern portion 32A and second excitation coil pattern portion 32B) in the above embodiment is an example, and is not limited to the shapes shown in Figures 8 and 9 as long as it is a shape that can generate an AC magnetic field that penetrates the excitation coil 32 along one direction D1.

[0115] In the above embodiment, the detection coil 33 includes the first detection coil pattern portion 33A disposed on the first layer 301 of the substrate 31 and the second detection coil pattern portion 33B disposed on the second layer 302 of the substrate 31. The detection coil 33 may be disposed only on the first layer (opposing surface 301) of the substrate 31.

[0116] Furthermore, the shapes of the detection coils 33 (first detection coil 331 and second detection coil 332) in the above embodiment are merely examples, and are not limited to the shapes shown in Figures 8 and 9 as long as they are shapes that can detect sine wave signals and cosine wave signals.

[0117] In the above embodiment, the rotor 2 has an end shaft structure (see Figure 1), but the rotor 2 may also have a structure in which, for example, a rotating shaft is inserted into a through hole in the rotor body and the rotor 2 is attached so as to rotate integrally with the rotating shaft.

[0118] In the above embodiment, the rotor 2 has four conductive portions 22, but the rotor 2 may have, for example, two, three, or five or more conductive portions 22.

[0119] (Summary) The present specification discloses the following aspects.

[0120] A rotation sensor (1) according to a first aspect is a sensor for detecting the rotation angle of a rotating object (4). The rotation sensor (1) includes a rotor (2) and a stator (3). The rotor (2) faces the rotor (2) in one direction (D1). The stator (3) is conductive and is attached to the rotating object (4) to rotate integrally with the rotating object (4). The stator (3) includes a substrate (31), an excitation coil (32), a detection coil (33), electronic components (34), a wiring pattern portion (35), and a ground conductor (36). The substrate (31) has a first main surface (301) facing the rotor (2) in the one direction (D1) and a second main surface (304) opposite the first main surface (301). The excitation coil (32) is disposed on the first main surface (301) of the substrate (31) to generate a magnetic field. The detection coil (33) is disposed on the first main surface (301) of the substrate (31) to detect changes in the magnetic field. The electronic component (34) is disposed on the second main surface (304) of the substrate (31). The wiring pattern portion (35) is electrically connected to the electronic component (34). The ground conductor (36) is disposed between the rotor (2) and the wiring pattern portion (35) in one direction (D1).

[0121] According to this aspect, even if the position of the rotor (2) fluctuates in one direction (D1) during operation of the rotation sensor (1), the ground conductor (36) can suppress fluctuations in the impedance of the wiring pattern portion (35). This makes it possible to stabilize the operation of the circuit of the rotation sensor (1). Therefore, according to this aspect, the rotation sensor (1) can be made smaller without reducing detection accuracy.

[0122] In the rotation sensor (1) according to the second aspect, in the first aspect, the rotating object (4) is a rotating shaft (4). The rotor (2) is attached to the tip of the rotating shaft (4) to rotate integrally with the rotating shaft (4), and faces the first main surface (301) of the substrate (31) in one direction (D1).

[0123] According to this embodiment, since the tip (rotor) of the rotating shaft (4) faces the first main surface (301) of the substrate (31), it is easier to arrange the electronic components (34) on the second main surface (304) of the substrate (31) than in a structure in which the rotating shaft penetrates the substrate. In other words, the space on the second main surface (304) of the substrate (31) can be effectively utilized, making it easier to miniaturize the rotation sensor (1).

[0124] In the rotation sensor (1) according to the third aspect, in the first or second aspect, the rotor (2) has a plurality of conductive portions (22) arranged along the rotation direction (DR1) of the rotor (2). A plurality of gaps (23) are provided to separate the plurality of conductive portions (22) from one another.

[0125] According to this aspect, the rotation sensor (1) as a whole can be made smaller and lighter.

[0126] In the rotation sensor (1) according to the fourth aspect, in any one of the first to third aspects, the ground conductor (36) is arranged on the first main surface (301).

[0127] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35), and therefore the rotation sensor (1) can be made smaller without reducing the detection accuracy.

[0128] In a rotation sensor (1) according to a fifth aspect, in any one of the first to fourth aspects, the excitation coil (32) is annularly arranged on the first main surface (301) along the outer edge (20) of the rotor (2) in a plan view from one direction (D1). The detection coil (33) is arranged inside the excitation coil (32) on the first main surface (301). The ground conductor (36) is arranged inside the detection coil (33) on the first main surface (301).

[0129] According to this aspect, the excitation coil (32), the detection coil (33), and the ground conductor (36) can be disposed on the first main surface (301) of the substrate (31), eliminating the need to unnecessarily increase the number of layers of the substrate (31). This prevents an increase in the weight of the substrate (31). The entire rotation sensor (1) can be made smaller and lighter.

[0130] In the rotation sensor (1) according to the sixth aspect, in any one of the first to fifth aspects, at least a part of the electronic component (34) is arranged in a position overlapping with the ground conductor (36) in one direction (D1).

[0131] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35), and therefore the rotation sensor (1) can be made smaller without reducing the detection accuracy.

[0132] In the rotation sensor (1) according to the seventh aspect, in any one of the first to sixth aspects, at least a part of the wiring pattern portion (35) is arranged in a position overlapping with the ground conductor (36) in one direction (D1).

[0133] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35), and therefore the rotation sensor (1) can be made smaller without reducing the detection accuracy.

[0134] In the rotation sensor (1) according to an eighth aspect, in any one of the first to seventh aspects, the wiring pattern portion (35) includes a first wiring pattern portion (351), a second wiring pattern portion (352), and a third wiring pattern portion (353). The first wiring pattern portion (351) electrically connects the electronic component (34) and the excitation coil (32). The second wiring pattern portion (352) electrically connects the electronic component (34) and the detection coil (33). The third wiring pattern portion (353) electrically connects the electronic component (34) and another electronic component (34). At least one of the first wiring pattern portion (351), the second wiring pattern portion (352), and the third wiring pattern portion (353) is arranged on the second main surface (304) of the substrate (31).

[0135] According to this aspect, even if the position of the rotor (2) fluctuates in one direction (D1) during operation of the rotation sensor (1), it is possible to suppress fluctuations in the impedance of the first wiring pattern portion (351), the second wiring pattern portion (352), and the third wiring pattern portion (353), thereby stabilizing the operation of the circuit of the rotation sensor (1).

[0136] In a rotation sensor (1) according to a ninth aspect, in any one of the first to eighth aspects, the ground conductor (36) includes a solid conductor. At least a portion of the wiring pattern portion (35) is disposed on the second main surface (304) of the substrate (31). In a plan view from one direction (D1), the area of ​​the electronic component (34) and the wiring pattern portion (35) on the second main surface (304) is smaller than the area of ​​the solid conductor.

[0137] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35), and therefore the rotation sensor (1) can be made smaller without reducing the detection accuracy.

[0138] In a rotation sensor (1) according to a tenth aspect, in any one of the first to ninth aspects, at least a portion of the wiring pattern portion (35) is disposed on the second main surface (304). The substrate (31) is a multilayer substrate having a plurality of layers (301) to (304). The ground conductor (36) is disposed on the first main surface (301) and at least one layer (301) to (303) of the plurality of layers (302) to (304).

[0139] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35) in the multilayer board, and therefore it is possible to reduce the size of the rotation sensor (1) without reducing the detection accuracy.

[0140] In a rotation sensor (1) according to an eleventh aspect, in any one of the first to tenth aspects, at least a portion of the wiring pattern portion (35) is arranged on the second main surface (304). The substrate (31) is a multilayer substrate having a plurality of layers (301) to (304). The excitation coil (32) includes a first excitation coil pattern portion (32A) arranged on the first main surface (301) and a second excitation coil pattern portion (32B) arranged on the layer (302) closest to the first main surface (301). The detection coil (33) includes a first detection coil pattern portion (33A) arranged on the first main surface (301) and a second detection coil pattern portion (33B) arranged on the layer (302) closest to the first main surface (301). The ground conductor (36) includes a first ground conductor pattern portion (36A) arranged on the first main surface (301) and a second ground conductor pattern portion (36B) arranged on at least one layer (302) of the plurality of layers (301) to (304).

[0141] According to this aspect, it is easy to suppress the fluctuation of the impedance of the wiring pattern portion (35) in the multilayer board, and therefore it is possible to reduce the size of the rotation sensor (1) without reducing the detection accuracy.

[0142] The configurations according to the second to eleventh aspects are not essential for the rotation sensor (1) and can be omitted as appropriate.

[0143] The rotation sensor of the present disclosure allows the rotation sensor itself to be miniaturized, and is thus industrially useful.

[0144] DESCRIPTION OF SYMBOLS 1 Rotation sensor 2 Rotor 3 Stator 4 Rotating object (rotating shaft) 20 Outer edge 22 Conductive portion 23 Gap 31 Substrate 32 Excitation coil 32A First excitation coil pattern portion 32B Second excitation coil pattern portion 33 Detection coil 33A First detection coil pattern portion 33B Second detection coil pattern portion 34 Electronic component 35 Wiring pattern portion 351 First wiring pattern portion 352 Second wiring pattern portion 353 Third wiring pattern portion 36 Ground conductor 36A First ground conductor pattern portion 36B Second ground conductor pattern portion 36C Third ground conductor pattern portion 36D Fourth ground conductor pattern portion 301 First layer (opposing surface) (first main surface) 302 Second layer 303 Third layer 304 Fourth layer (opposite surface) (second main surface) D1 One direction DR1 Rotation direction RC1 Rotation center

Claims

1. A rotation sensor that detects the rotation angle of a rotating object, comprising: a rotor that is conductive and attached to the rotating object to rotate integrally with the rotating object; and a stator that faces the rotor in one direction, wherein the stator comprises: a substrate having a first main surface that faces the rotor in the one direction and a second main surface opposite the first main surface; an excitation coil that is disposed on the first main surface of the substrate and generates a magnetic field; a detection coil that is disposed on the first main surface of the substrate and detects changes in the magnetic field; electronic components that are disposed on the second main surface of the substrate; a wiring pattern portion that is electrically connected to the electronic components; and a ground conductor that is disposed between the rotor and the wiring pattern portion in the one direction.

2. The rotation sensor according to claim 1, wherein the rotating object is a rotation shaft, and the rotor is attached to the tip of the rotation shaft to rotate integrally with the rotation shaft, and faces the first main surface of the substrate in the one direction.

3. The rotation sensor according to claim 2, wherein the rotor has a plurality of conductive parts arranged along the direction of rotation of the rotor, and a plurality of gaps are provided to separate the plurality of conductive parts from one another.

4. The rotation sensor according to claim 1, wherein the ground conductor is disposed on the first main surface.

5. A rotation sensor as described in claim 1, wherein the excitation coil is arranged in a ring shape on the first principal surface so as to follow the outer edge of the rotor when viewed in a plane from the one direction, the detection coil is arranged inside the excitation coil on the first principal surface, and the ground conductor is arranged inside the detection coil on the first principal surface.

6. The rotation sensor according to claim 1, wherein at least a portion of the electronic component is disposed in a position overlapping the ground conductor in the one direction.

7. The rotation sensor according to claim 1, wherein at least a portion of the wiring pattern portion is disposed in a position overlapping the ground conductor in the one direction.

8. A rotation sensor as described in claim 1, wherein the wiring pattern portion includes a first wiring pattern portion, a second wiring pattern portion, and a third wiring pattern portion, the first wiring pattern portion electrically connecting the electronic component and the excitation coil, the second wiring pattern portion electrically connecting the electronic component and the detection coil, and the third wiring pattern portion electrically connecting the electronic component and another electronic component, and at least one of the first wiring pattern portion, the second wiring pattern portion, and the third wiring pattern portion is arranged on the second main surface of the substrate.

9. A rotation sensor as described in claim 1, wherein the ground conductor includes a solid conductor, at least a portion of the wiring pattern portion is disposed on the second main surface of the substrate, and when viewed in a plan view from the one direction, the area of ​​the electronic component and the wiring pattern portion on the second main surface is smaller than the area of ​​the solid conductor.

10. A rotation sensor as described in claim 1, wherein at least a portion of the wiring pattern portion is disposed on the second main surface, the substrate is a multilayer substrate having a plurality of layers, and the ground conductor is disposed on the first main surface and on at least one of the plurality of layers.

11. A rotation sensor as described in claim 1, wherein at least a portion of the wiring pattern portion is arranged on the second main surface, the substrate is a multilayer substrate having a plurality of layers, the excitation coil includes a first excitation coil pattern portion arranged on the first main surface and a second excitation coil pattern portion arranged on a layer closest to the first main surface, the detection coil includes a first detection coil pattern portion arranged on the first main surface and a second detection coil pattern portion arranged on a layer closest to the first main surface, and the ground conductor includes a first ground conductor pattern portion arranged on the first main surface and a second ground conductor pattern portion arranged on at least one layer of the plurality of layers.

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